Unable-to-Add-a-Directory-to-Play-Local-Files-linux -- still not working - Ubuntu 17.10

[tdelprat]

Trying to add a local folder in the Linux Desktop Spotify App

Preferences > Local Files > Add a Source

But nothing happens: pretty much as described in 
https://community.spotify.com/t5/Desktop-Linux/Unable-to-Add-a-Directory-to-Play-Local-Files-linux/m....

I know the previous thread is marked as solved but the "solution" does not work - at all.

Starting Spotify from the command line, I can see that when I click on the button "Add a File" there is an error displayed in the console.

Gtk-Message: GtkDialog mapped without a transient parent. This is discouraged.
Segmentation fault (core dumped)

Hope this helps.